Differential apparatus for automatically filling well casing



May 7, 195 E. H. cLARk, JR 2,791,279

DIFFERENTIAL APPARATUS FOR AUTOMATICALLY FILLING WELL CASING Filed Oct. 25, 1954 2 Sheets-Sheet 1 B pflyug.

522N557 fl. 6LAEK J22.

INVE'NTOR.

ATfOE/VEYS May 7, 1957 Filed Oct. 25. 1954 E. H. CLARK, JR 2,791,279 DIFFERENTIAL APPARATUS FOR AUTOMATICALLY FILLING WELL CASING 2 Sheets-Sheet. i2

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39 IN VEN TOR.

ATTQENEYS United States Patent DIFFERENTIAL APPARATUS FGR AUTOMATI- CALLY FILLING WELL CASENG Earnest H. Clark, Jr., Downey, Califl, assignor to Baker Oil Tools, Inc., Los Angeles, Calif., a coporation of California Application October 25, 1954, Serial No. 464,408

11 Claims. (Cl. 166-225) The present invention relates to valve devices for con-- trolling the flow of fluid, and more particularly to valve devices for controllably filling a string of well casing, or similar well conduit, as it is lowered through the fluid in the well bore.

The valve apparatus is employed in the lower end of the string of well casing, or similar well conduit, to control the rate at which the fluid in the well bore can flow into the casing as it is lowered in the well bore and also to prevent the fluid from rising in the well casing above a level that is lower than the fluid level in the well bore externally of the Well casing. During the running of the casing string in the well bore, the valve apparatus opens and closes repeatedly. The initial opening of the valve and its final closing have heretofore been accompanied by a throttling action or restriction on the flow of fluid through the valve, attended by erosion by the fluid on the valve parts, which sometimes causes their failure. Such erosive or fluid cutting action is most pronounced on the coengaging valve head and valve seating surfaces, resulting sometimes in valve leakage when the valve should provide a full closing action. Such leakage may forestall the maintenance of the fluid level internally of the casing at a predetermined lower point than the fluid level externally of the casing.

An object of the present invention is generally to increase the life of the valve parts by minimizing the cutting action of the fluid flowing through the valve on 1 the coengaging surfaces of the valve head and companion valve seat.

Another object of the invention is to insure a more open position, thereby reducing the opportunity for fluidflowing through the valve to erosively wear its parts.

A further objectof the invention is to insure the maintenance of the valve in a fully closed position by the application of a greater total hydraulic holding force thereon than is available to move the valve toward its closed position.

Yet another object of the invention is to provide an improved apparatus for controllably filling a string of well casing, and the like, while it is being lowered in the well bore, in which the fluid externally of the well casing is instrumental in opening the valve, the total hydraulic force available for moving the valve to a fully open position being substantially greater than the hydraulic force available to effect initial movement of the valve toward open position, thereby causing the valve to be shifted rapidly to a fully open position.

This invention possesses many other advantages and has other objects which may be made more clearly apparent from a consideration of a form in which it may be embodied. This form is shown in the drawings accompanying and forming part of the present specification. It will now be described in detail, for the purpose of illustrating the general principles of the invention; but it is to be understood that such detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

disposed within the tubular member.

cementitious material is cast.

Referring to the drawings:

Figure 1 is a longitudinal section through an apparatus embodying the invention, with the valve mechanism disposed in closed position to prevent upward flow of fluid in the casing string;

Fig. 2 is a view similar to Fig. 1, disclosing the valve mechanism in open position to permit upward flow of fluid in the casing string;

Fig. 3 is a view similar to Fig. 1, disclosing the internal mechanism in a position permitting downward flow of fluid through the apparatus;

Fig. 4 is a view similar to Fig. 1, disclosing the valve mechanism acting as a back pressure valve to prevent return flow of fluid in the casing string;

Fig. 5 is an enlarged fragmentary longitudinal section through a portion of the valve mechanism, the valve being in its downward closed position.

point in the casing, in which event it would be considered to be a casing collar forming part of the casing string. In addition, the apparatus could be incorporated in other conduit strings to be lowered through fluid in a well bore. As disclosed, the casing shoe A includes an outer tubular member which may have an upper threaded box 11 threadedly secured to the lower pin end 12 of an adjacent casing section B. A valve mechanism is This mechanism is of the type which will allow the fluid in the well bore to flow upwardly into the casing string B while the latter is being lowered in the well bore. But when the casing string has been lowered to the desired extent in the well bore, the valve mechanism can be placed in a condition in which it can preclude upward flow of fluid in the well casing, while permitting fluid to be pumped down through the well casing B and out through the casing shoe A.

The valve mechanism is constituted by an outer housing or valve body 13 which is secured to the tubular member 10 through the agency of an intermediate cementitious plug 14. This plug is inseparably united to the spaced circumferential grooves 15 therein, in which the cementitious material is cast. The lower end 16 of the cement plug is rounded or tapered, to provide 'a guiding nose for the shoe, in order to appropriately steer the casing past restrictions or obstructions that might be encountered in-the well bore during its lowering therewithin. The outer housing 13 is also provided with longitudinally spaced circumferential external grooves 17 in which The upper end of the cement plug 14, as well as its lower end, has a passage 18 therethrough through which fluid can flow.

For convenience of assembling the apparatus, the valve housing or body 13 is made in several sections. Thus, an upper section 19 is disposed in the cementitious plug and has an annular seal ring 20 clamped thereagainst by spider having a central hub connected to the outer portion of the lower section by a plurality of circumferentially spaced ribs 26, these ribs defining openings 27 therebetween through which fluid can pass.

-A valve stem or guide 28 has its lower portion 29 slidable through the spider hub 25, this stern having an intermediate enlarged portion 30 providing a downwardly facing shoulder 31 that initially rests on the upper end of the hub 25 to prevent downward movement of the valve stem or guide 28. Upward movement of the valve stem or guide is prevented initially by piloting the upper portion of the enlarged stem section within the hub 32 of a holding or stop spider 33 slidably engageable with the cylindrical wall 34 of the intermediate and lower housing sections 23, 24. An annular valve seat structure 35 rests upon the outer portion 36 of the holding spider, this seat structure being prevented from moving in an upward direction by engaging a shoulder 37 provided on the intermediate housing section 23.

The annular valve seating structure 35 is made in several parts for convenience of assembly. Thus, it includes an upper seat section 60 having a downwardly directed skirt 61 engaging the stop spider 33, and also the shoulder 37 on the intermediate housing section 23. Leakage of fluid around this upper seating section is prevented by a seal ring 62, in the form of a rubber ring, engaging its periphery and carried within a circumferential groove 63 in the intermediate housing section. A lower seat section 64 is disposed within the skirt portion 61 of the upper seat section in abutting relation to the upper seat section, this lower seat section engaging the upper end of the stop spider 33. The lower seat section 64 has an inwardly projecting relatively sharp edge seat 65 adapted to be engaged by a downward and inwardly tapering surface 66 on the lower portion 67 of the valve head 22, in order to close the valve against upward passage of fluid therethrough. Above the knife or sharp edge 65 of the lower valve seat 64, the latter and the upper valve seat 60 are provided with an internal cylindrical seating surface 63 which is adapted to be slidably engaged by a companion external cylindrical periphery 69 of the valve head 22.

To increase the life of the parts, the tapered and cylindrical surfaces 66, 69 on the valve head are formed on a separate ring insert 67, that may be made of relatively hard metal suitably secured to the remaining portion of the valve head or valve member 22. The valve seat sections 60, 64 are likewise formed of relatively hard metal, such as cast iron.

T 0 further insure against leakage between the cylindrical periphery 69 of the valve head insert 67 and the cylindrical seat 68, a seal ring 70, such as a rubber 0 ring, may be disposed in a ring groove 71 formed between the upper and lower seat sections 60, 64, the seal ring being adapted to sealingly engage the cylindrical periphery 69 of the valve seat insert 67.

From the valve head and valve seat construction so far described, it is evident that there are actually two valve portions to close the valve device. The valve closing elements are provided by the engagement of the tapered surface 66 on the valve head 22 with the metallic sharp seat 65 on the valve seating structure 35, whereas another closing surface is provided by the engagement of the cylindrical periphery 69 on the valve head with the cylindrical seat 68 provided on the seating structure. The closing action between the latter surfaces may be enhanced, if found necessary, by the incorporation of the rubber seal ring 70 in the seating structure slidably and sealingly engaging the cylindrical periphery 69 of the valve head member. The sharp edge 65 on the valve seat 64 engages the tapered surface 66 on the valve head,

and is found to close more efficiently and effectively than if a surface contact were provided between the tapered portion 66 ofthe valve head 22 and the lower seat section 64. Moreover, it is found that there is less fluid cutting action on the valve parts with the sharp metalto-metal seating engagement between the lower seat section 64 and the tapered surface 66 of the valve head.

It will be noted that the hub 32 of the holding spider initially has an inwardly directed flange 38 disposed across valve seat.

and in contact with the upwardly facing shoulder 39 of the valve guide 28. In view of such engagement, the valve guide 28 is prevented from moving upwardly by the holding spider 33, and this spider, in turn, is prevented from moving upwardly within the housing 13 by virtue of its engagement with the valve seat structure 35 that, in turn, engages the shoulder 37 of the intermediate housing section 23. Similarly, the valve seat structure 35 cannot move downwardly of the housing by engaging the holding spider 33, and the latter cannot move downwardly of the housing by virtue of its flange 38 engaging the guide 28, the downwardly facing shoulder 31 of the latter engaging the lower spider 24. With the parts arranged in this fashion, the valve guide 28, upper spider 33, and the valve seat structure 35 are initially prevented from moving in either longitudinal direction. The valve head or member 22, however, can move in both an upward and a downward direction with respect to the valve guide 28 and the valve seat structure 35. This valve head is disposed between the upper and lower seats 20, 35 and is adapted to selectively engage these seats.

The valve head 22 has a central downwardly opening bore 39 to receive the upper piston portion 40 of the valve stem or guide 28. The bore constitutes a cylinder in which the piston is slidable, the piston preferably carrying one or more piston rings or side seals 41 sealingly engaging the inner wall 42 of the bore cylinder, to prevent the well bore fluid from entering the cylinder 39 above the piston 40. The cylinder above the piston is thereby maintained free of well bore fluid and will initially contain air at substantially atmospheric pressure, the upper portion of the valve head 22 and end wall 43 constituting a closure for the cylinder or bore.

The valve head 22 is movable downwardly, to engage its tapered surface 66 with the sharp seating surface on the annular valve seat, and also to place its cylindrical periphery 69 in engagement with the cylindrical seat portion 68 of the seating structure 35. When the parts are so engaged, fluid is prevented from passing downwardly between the valve head 22 and the seating structure 35. The valve head 22 can slide upwardly along the piston 40 to allow fluid to flow in an upward direction through the upper and lower spiders 24, 33, and through the valve seat structure 35, passing around the exterior of the valve head 22 and on up through the central passage 18 into the casing string B thereabove. Initially, the valve head 22 is prevented from moving upwardly into engagement with the upper valve seat ring 20 by a suitable stop element in the form of a ring 72 clamped to the valve head 22 by a retainer member 73 threaded on the valve head and engaging the underside of the stop ring. The stop ring 72 extends inwardly into the bore 39 of the valve head and is engageable with the lower end of the piston 40.

When the valve head 22 is fully engaged with both the cylindrical and sharp seats 68, 65, the fluid in the well casing is acting in a downward direction over the crosssectional area S of the valve head, which area extends to the cylindrical periphery of the latter. In view of the closed cylinder 39, which contains air at substantially atmospheric pressure, the fluid under pressure below the valve head 22 is acting in an upward direction over the annular cross-sectional area R of the valve head lying between the inner cylindrical wall 42 of the head and its line of contact with the sharp edge 65 of the lower It is evident that the fluid within the well casing B is acting over a substantially greater pressure elfective area than the fluid externally of the well casing and below the valve head 22. Accordingly, the valve head 22 will be shifted downwardly into engagement with its seat when the pressure inside the well casing B is lower than the pressure externally of the well casing, the internal pressure being proportional to the external pressure in the ratio of the lower pressure effective annular area R to the upwardly facing pressure effective crosssectional area S of the valve head.

With the relationship of the parts so far-described, the valve head 22 is only effective to move out of engagement from its seats and back into engagement with these seats, to either permit upward flow of fluid into the apparatus or to prevent downward flow of fluid in the apparatus. Such mode of action is desirable during lowering of the casing string through the fluid in the well bore. However, following the arrival of the casing string at its desired depth in the well bore, fluid is to be pumped down through the casing B and out through the casing shoe A. When this occurs, the apparatus is operated, to allow fluid to be pumped in a downward direction therethrough and it is also placed in condition wherein the valve head 22 can move upwardly to a suflicient extent to engage the upper valve seal and prevent upward passage of fluid back into the casing string B.

To accomplish the purposes just noted, the inwardly directed flange 38 of the upper spider hub 32 is made disruptable. That is to say, it can be sheared from the main portion of the hub along the circumferential area 50, which will then allow the upper spider 33 and the lower seating structure 35 to drop downwardly within the intermediate and lower housing sections to a substantial extent (Fig. 3). The valve head 22 cannot move downwardly as far as the lower seating structure 35, in view of the engagement of its end wall 43 with the upper end of the piston 40. Accordingly, there will be a longitudinal space between the valve head 22 and the lower seating structure 35 through which fluid can pass in a downward direction, the fluid continuing on through the lower seating structure 35 and through the spiders 33, 24 into the lower passage portions 18 through the cement plug 14 and on out of the well casing.

, Because of the shearing of the inner flange 38 from the main body of the upper spider hub 32, the valve stem is no longer restrained against upward movement. Accordingly, should fluid tend to flow upwardly through the casing shoe A, it will carry the valve head 22 in an upward direction toward the upper seat and seal 29, the stop ring 72 engaging the lower end of the piston 4-6 and lifting the valve stem or guide 28 with it to the extent required for the valve head 22 to engage the upper seat 20.

In the operation of the apparatus, the parts are arranged in the manner disclosed in Fig. 1, in which the valve guide 28 is prevented from moving in both longitudinal directions, the lower valve seat structure 35 being held in its upper position. As the well casing B is lowered through the fluid in the well bore, the hydro static head of fluid externally of the casing string can act on the downwardly facing surfaces of the valve head 22 to elevate it from the seating structure to the extent limited by engagement of the stop ring 72 with the lower end of the piston (Fig. 2). When the head is in this position, it is still prevented from engaging the upper seat 2%). Accordingly, the fluid in the well bore can flow through the spider 24, 33 and through the lower valve seat structure 35, passing around the head 22 and through the upper valve seat 29 into the central passage 18 in the casing string B. When the fluid in the well casing reaches a predetermined level, which will be less than the level of the fluid in the well bore externally of the well casing, such fluid will be effective over the greater upwardly projected area S of the valve head 22,to shift itdownwardly into sealing engagement with the valve seating structure 35, such as disclosed in Fig. 1, whereupon further upward passage of fluid is precluded. However, as the well casing is lowered to a greater depth, the valvewillagain be opened (Fig. 2), to allow'the well casing to fill with additional fluid, 'in'ord'er to maintain the ratio of fluid level corresponding to the ratio of downwardly facing and upwardly facing areas R', S,

over which the external and internal fluid pressures are acting.

When the well casing has been lowered to the desired depth in the well bore, the casing string can be filled completely with fluid at the top of the hole, whereupon pressure is applied to this fluid. This pressure acts in a downward direction over the cross-sectional area S of the 'valve head 22 and also over the annular area of the valve seat structure 35, these parts exerting a combined downward force on the upper spider 33. When the pressure is sufficient, the downward force will shear the inwardly directed flange 38 from the main body of the upper spider hub 32, the fluid under pressure within the well casing then being effective to shift the head 22, seating structure 35 and the upper spider 33 downwardly within the housing 13 (Fig. 3). The upper spider 33 and valve seating structure 35 will move downwardly to the extent determined by engagement of the upper spider with the lower spider 24. However, the valve head 22 cannot move this great a distance because its end wall 43 engages the upper end of the piston 40, so that a substantial longitudinal space remains between the lower portion 44 of the valve head and lower seating structure 35 through which fluid can flow. Fluid within the well casing can now pass downwardly through the casing shoe A, discharging therefrom and then passing in an upward direction through the annulus between the exterior of the-well casing B and the wall of the well bore. If desired, a charge of cement slurry or corresponding cementitious material may now be pumped down the casing string, passing through and from the casing shoe for disposition around and behind the string of well casing.

In the event the pressure within the well casing is relieved and fluid tends to pass back into the well casing, this fluid will shift the valve head 22 and the valve stem 28 in an upward direction until the valve head engages the upper valve seat 20, thereby closing the passage 18 against upward passage of fluid therethrough. The upward movement of the valve head 22 to the extent just indicated is no longer prevented by engagement of the stop ring with the lower end of the piston 40, inasmuch as the shearing of the flange 38 on the upper spider hub 32 removes the restraint to upward movement on the valve guide or stem 28.

At any time, fluid can be pumped downwardly through the shoe A, the valve head 22 being merely shifted off its upper seat 20. This head will again reengage the seat 26 in the event upward passage of fluid tends to occur.

The provision of the two different valve seats 65, 68 which are engaged with two different portions 66, 69 of the valve head 22 greatly increases the life of the valve part and reduces, if not eliminating entirely, the erosive effect of the fluid flowing between the lower tapered portion 66 of the valve head and the sharp edge valve seat 65. Assuming that only the tapered surface 66 of the valve head and the sharp valve seat were available to close the valve, the initial upward movement of the valve head 22, when the valve opens, would allow fluid to flow between the head surface 66 and seat 65, this fluid being throttled and having a relatively high velocity. As a result, the coengageable valve parts 65, 66 would become fluid cut and would be incapable of fully closing the valve when the valve head 22 moves back down into engagement with the seat 65.

Because of the construction described above, when the valve head 22 begins to move upwardly, to remove its tapered surface 66 from engagement with the valve seat 65, substantially no fluid can flow between these parts, inasmuch as the cylindrical surface 69 on the valve head is still in sealing relation to the cylindrical valve seat 68 (and the 0 ring seal, if used). The fluid flow can only occur when the valve head 22 is moved upwardly sufficiently to bring the cylindrical periphery 69 of the valve head above the cylindrical seat 68 on the valve seat struce substantial distance above the relatively sharp valve seat '65. Accordingly, there is a substantially great area between these parts through which the fluid will flow, and such flow will occur at a relatively low velocity, which will be incapable of eroding the parts. It may well be that some erosion wear may occur at the upper portion of the cylindrical seat 68, but even were this to occur, the net result would merely be the tendency for fluid to pass between the cylindrical seat 68 and the cylindrical portion 69 of the valve head 22 when the valve is fully closed. However, the tapered surface 66 of the valve head and its companion valve seat 65 would be intact, and would prevent fluid leakage therebetween when coengaged.

Similarly, when the valve head 22 moves downwardly toward a closed position, the fluid flow between the head and valve seat structure 35 is substantially entirely stopped when the lower end of the cylindrical periphery 69 of the valve head enters the cylindrical valve seat 68. At this time, the tapered valve head surface 66 is disposed a substantial distance above the lower seat 65, which will pre vent these parts from being fluid cut as a result of the throttling action of the cylindrical portions 68, 69 of the apparatus on the flow of fluid through the valve when the cylindrical portion 69 of the valve head is closely adjacent and above the cylindrical seat 68. The flow of fluid is substantially entirely arrested when the cylindrical periphery 69 of the valve head enters the cylindrical seat 68, so that the continued downward movement of the valve head within the seating structure will bring the tapered surface 66 of the valve head into engagement with the sharp edge seat 65 under conditions in which no flow of fluid is occurring through the valve device. Accordingly, the lower seat 65 and tapered portion 66 of the valve head 22 do not impose any restrictions to the flow of fluid through the apparatus, which would be conducive to erosive wear on the parts.

The valve seating structure 35 and the valve head 22 cooperating therewith not only have the effect of preventing leakage through the valve mechanism because of erosive wear on the parts, but it is also instrumental in securing a quick shifting of the valve head 22 to a fully open position, and insures the retention of the valve head in a downward closed position.

It is to be noted that the fluid externally of the well casing, or below the valve head 22, i acting in an upward direction on the valve head tending to shift it to open position over the annular area R, when the valve head is in engagement with the knife-like seat 65. However, as soon as the valve head 22 moves slightly off this knife-edge seat 65, the fluid under pressure acting in an upward direction on the valve head has an additional area over which to operate, which is the annular area T between the knife-edge seat and the cylindrical seat 68 of the valve seating structure. In other words, although movement of the valve head 22 in an upward direction for the purpose of opening the valve is initiated with the fluid pressure acting over the area R only, once the initial elevation of the valve head occurs to a relatively minute or small extent, the fluid pressure is effective to act over the sum of the areas R and T, which will result in a rapid elevation of the valve head to its fully open position (Fig. 2), giving the fluid a much lesser opportunity and time to impose any erosive action on the companion cylindrical surfaces 68, 69 f the apparatus when the cylindrical portion 69 of the valve head moves above the cylindrical valve seat 68.

As the string of well casing fills with the fluid, with the valve in fully open position, and approaches the predetermined level within the casing string at which the valve head 22 will be shifted downwardly by virtue of the fluid acting over the area S of the valve head, the fluid pressure acting in an upward direction over the valve head and resisting the closing action is operating over the combined areas of R and T. However, once the head 22 has moved downwardly, to place its tapered surface 66 in engagement with the lower sharp seat 65, then the fluid force resisting closing of the valve is effective to act only over the area R, so that there is a greater total resultant force available to hold the valve in closed position than is available to move the valve toward a fully closed position. The valve can be shifted again to open position only when the hydrostatic head of fluid externally of the string of well casing is greater than the hydrostatic head of fluid internally of the well casing by the proportion that the area S bears to the area R.

The inventor claims:

1. In apparatus of the character described: a tubular member having a longitudinal passage therethrough and adapted to be secured to a conduit section to be disposed in a well bore; a first valve seat in said tubular member; a second valve seat in said tubular member above said first valve seat; a fluid actuated valve member having a first portion engageable with said first valve seat upon downward movement of said valve member in said tubular member to close said passage, said valve member having a second portion engageable with said second valve seat upon downward movement of said valve member in said tubular member to substantially close said passage substantially prior to engagement of said first portion with said first valve seat; said valve member having a total resultant upwardly facing cross-sectional area subject to the pressure of fluid above said valve member which is greater than the total resultant downwardly facing crosssectional area of said valve member subject to the pressure of fluid below said valve member when said first valve member engages said first valve seat, said upwardly facing cross-sectional area also being greater than the total resultant downwardly facing cross-sectional area of said valve member subject to the pressure of fluid below said valve member when said first portion is disengaged from said first valve seat; said last-mentioned downwardly facing cross-sectional area being greater than said first-mentioned downwardly facing cross-sectional area.

2. In apparatus of the character described: a tubular member having a longitudinal passage therethrough and adapted to be secured to a conduit section to be disposed in a well bore; a first valve seat in said tubular member; a second valve seat in said tubular member above said first valve seat; a fluid actuated valve member having a first portion engageable with said first valve seat along a circumferential line of contact only upon downward movement of said valve member in said tubular member to close said passage, said valve member having a second portion engageable with said second valve seat upon downward movement of said valve member in said tubular member to substantially close said passage substantially prior to engagement of said first portion with said first valve seat.

3. In apparatus of the character described: a tubular member having a central passage therethrough and adapted to be secured to a conduit section to be disposed in a well bore; a first valve seat in said tubular member; a second cylindrical valve seat in said tubular member above said first valve seat; a fluid actuated valve member having a first portion engageable with said first valve seat upon downward movement of said valve member in said tubular member to close said passage; said valve member having a second cylindrical portion engageable with said second cylindrical valve seat upon downward movement of said valve member in said tubular member to substantially close said passage substantially prior to engagement of said first portion with said first valve seat; said valve member having a total resultant upwardly facing cross-sectional area subject to the pressure of fluid above said valve member which is greater than the total resultant downwardly facing cross-sectional area of said valve member subject to the pressure of fluid below said valve member when said first portion engages said first valve seat, said upwardly facing cross-sectional ber when said first portion is disengaged (from said first valve seat; said last-mentioned downward-1y facing crosssectional area being greater than said first-mentioned downwardly facing cross-sectional area.

4. In apparatus of the character described: a tubular member having a central passage therethrough and adapted to be secured to a conduit section to be disposed in a well bore; a first valve seat in said tubular member; a second cylindrical valve seat in said tubular member above said first valve seat; (a fluid actuated valve memher having a first portion engageable with said first valve 4 seat along a circumferential line of contact only upon downward movement of said valve member in said tubular member to close said passage; said valve member having a second cylindrical portion engageable with said second cylindrical valve seat upon downward movement or said valve member in said tubular member to substantially close said passage substantially prior to engagement of said first portion with said first valve seat.

5. In apparatus of the character described: a tubular member having a longitudinal passage therethrough and adapted to be secured to a conduit section to be disposed in a well bore; a first valve seat in said tubular member; a second valve seat in said tubular member downstream of said first valve seat; a fluid actuated valve member having a first portion engageable with said first valve seat upon movement in an upstream direction of said valve member in said tubular member to close said passage; said valve member having a second portion engageable with said second valve seat upon movement in an upstream direction of said valve member in said tubular member to substantially close said passage substantially prior to engagement of said first passage with said first valve seat; said valve member having a total resultant downstream facing cross-sectional area subject to the pressure of fluid downstream of said valve member which is greater than the total resultant upstream facing crosssectional area of said valve member subject to the pressure of fluid upstream of said valve member when said first portion engages said first valve seat, said downstream facing cross-sectional area also being greater than the total resultant upstream facing cross-sectional area of said valve member subject to the pressure of fluid upstream of said valve member when said first portion is disengaged from said first valve seat; said last-mentioned upstream facing cross-sectional area being greater than said first-mentioned upstream facing cross-sectional area.

6. In apparatus of the character described: a tubular member having a longitudinal passage therethrough and adapted to be secured to a conduit section to be disposed in a well bore; a first valve seat in said tubular member; a second cylindrical valve seat in said tubular member downstream of said first valve seat; a fluid actuated valve member having a first portion engageable with said first valve seat upon upstream movement of said valve member in said tubular member to close said passage; said valve member having a second cylindrical portion engage able with said second cylindrical valve seat upon upstream movement of said valve member in said tubular member to substantially close said passage substantially prior to engagement of said first portion with said first valve seat; said valve member having a total resultant downstream facing cross-sectional area subject to the pressure of fluid downstream of said valve member which is greater than the total resultant upstream facing cross-sectional area of said valve member subject to the pressure of fluid upstream of said valve member when said first portion engages said first valve seat, said downstream facing crosssectional area also being greater than the total resultant upstream facing cross-sectional area of said valve member subject to the pressure of fluid upstream of said valve member when said first portion is disengaged from said first valve seat; said last-mentioned upstream facing crosssectional area being greater than said first-mentioned upstream facing cross-sectional area.

'7. in appauatus of the character described: a tubular member having a longitudinal passage therethrough and adapted to be secured to a conduit section to be disposed iin a well bore; a first valve seat in said tubular member;

a second internal cylindrical valve seat in said tubular member above said first valve seat; a fluid actuated valve member having a first portion engageable with said first valve seat along a circumferential line of contact only upon downward movement of said valve member in said tubular member to close said passage; said valve member having a second external cylindrical portion adapted to move within and en-gageable with said second internal cylindrical valve seat upon downward movement of said valve member in said tubular member to substantially close said passage substantially prior to engagement of said first portion with said first valve seat; the diameter of said internal valve seat being greater than the diameter of said first valve seat.

8. In apparatus of the character described: a tubular member having a longitudinal passage therethrough and adapted to be secured to a conduit section to be disposed in a well bore; a first valve seat in said tubular member; a second internal cylindrical valve seat in said tubular member above said first valve seat; a fluid actuated valve member having a first portion engageable with said first valve seat along a circumferential line of contact only upon downward movement of said valve member in said tubular member to close said passage; said valve member having a second external cylindrical portion adapted to move within and engageable with said second internal cylindrical valve seat upon downward movement of said valve member in said tubular member to substantially close said passage substantially prior to engagement of said first portion with said first valve seat.

9. In apparatus of the character described: a tubular member having a central passage therethrough and adapted to be secured to a conduit section; a first valve seat in said tubular member; a second internal cylindrical valve seat in said tubular member above said first valve seat; a guide member within and carried by said tubular member; a valve member telescoped over and slidable longitudinally along said guide member; said valve member having a first portion engageable with said first valve seat upon downward movement of said valve member in said tubular member to close said passage; said valve member having a second external cylindrical portion movable Within and engageable with said second internal cylindrical valve seat upon downward movement of said valve member into said tubular member to substantially close said passage substantially prior to engagement of said first portion with said first valve seat; the diameter of said internal cylindrical valve seat being greater than the diameter of said first valve seat.

10. In apparatus of the character described: a tubular member having a longitudinal passage therethrough and adapted to be secured to a conduit section to be disposed in a well bore; a first internal sharp edge valve seat in said tubular member; a second internal cylindrical valve seat in said tubular member above said first valve seat; a fluid actuated valve member having a surface inclined inwardly and downwardly and engageable with said first valve seat along a circumferential line of contact only upon downward movement of said valve member in said tubular member to close said passage; said valve member having a second external cylindrical portion movable within and engageable with said second valve seat upon downward movement of said valve member in said tubular member to substantially close said passage substantially prior to engagement of said inclined surface with said first valve seat; said internal cylindrical valve seat hav 11 ing a diameter substantially greater than the diameter of said first sharp edge valve seat.

11. In apparatus of the character described: a tubular member having a longitudinal passage therethrough and adapted to be secured to a conduit section to be disposed in a Well bore; a first valve seat in said tubular member; a second internal cylindrical valve seat in said tubular member above said first valve seat; a guide member within and carried by said tubular member; a valve member telescoped over and slidable longitudinally along said guide member into and out of engagement with said seat; said valve member having a surface inclined inwardly and downwardly and engageable with said first valve seat upon downward movment of said valve member in said tubular member to close said passage; said valve member 15 2,655,934

having a second external cylindrical portion movable within and engageable with said second valve seat upon 7 downward movement of said valve member in said tubular References Cited in the file of this patent UNITED STATES PATENTS 391,431 Shoff Oct. 23, 1888 1,951,037 Patterson Mar. 13, 1934 2,023,189 Armstrong Dec. 3, 1935 Clair Oct. 20, 1953 

